Vocal acoustic characteristics of patients with Parkinson's disease.

Speech samples obtained from 39 idiopathic Parkinson's disease (PD) patients with vocal pathologies were compared with those from 62 age-matched vocally normal non-PD controls. Voice samples collected from sustained vowel phonation and passage reading were acoustically analyzed using Computer Speech Lab and Multi-Dimensional Voice Program software. Noise-to-harmonic ratio, voice turbulence index (VTI) and soft phonation index (SPI) were incorporated as noise-related measurements, fundamental frequency-tremor intensity index (FTRI), amplitude tremor intensity, fundamental frequency-tremor frequency (Fftr), and amplitude-tremor frequency as tremor-related measurements. Compared with controls, the following results were noted: (1) male and female PD patients exhibited significant differences in acoustic parameters of all frequency and amplitude perturbation measurements and noise-related measurements (except VTI in males); (2) speaking fundamental frequency was significantly higher only in male PD patients; (3) FTRI and Fftr in male (only FTRI in female) PD patients were significantly higher, and (4) disease severity and MDVP analysis showed significant correlations between SPI and the Unified Parkinson's Disease Rating Scale Part I (mentation, behavior, mood) and Part II (activities of daily living) in male PD patients; however, this was not the case in female PD patients.